U.S. patent application number 12/285678 was filed with the patent office on 2009-05-07 for multichannel potentiostat having an adjustable counter-electrode potential.
This patent application is currently assigned to COMMISSARIAT A L'ENERGIE ATOMIQUE. Invention is credited to Alain Bourgerette, Gilles Marchand.
Application Number | 20090114537 12/285678 |
Document ID | / |
Family ID | 39434313 |
Filed Date | 2009-05-07 |
United States Patent
Application |
20090114537 |
Kind Code |
A1 |
Bourgerette; Alain ; et
al. |
May 7, 2009 |
Multichannel potentiostat having an adjustable counter-electrode
potential
Abstract
The multichannel potentiostat comprises a reference terminal, a
counter-electrode terminal, and at least two working terminals,
respectively designed to be connected to a reference electrode, a
counter-electrode and at least two working electrodes of an
electrochemical cell. The potentiostat comprises first and second
regulating circuits to apply a setpoint voltage respectively
between the first and second working terminals and the reference
terminal. The potentiostat comprises a control circuit of the
counter-electrode voltage applied to the counter-electrode
terminal. The control circuit comprises a first input terminal
connected to a predefined potential and a second input terminal to
which a regulating voltage representative of at least one of the
voltages of the working terminals is applied.
Inventors: |
Bourgerette; Alain; (Villard
Bonnot, FR) ; Marchand; Gilles; (Pierre-Chatel,
FR) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 320850
ALEXANDRIA
VA
22320-4850
US
|
Assignee: |
COMMISSARIAT A L'ENERGIE
ATOMIQUE
Paris
FR
|
Family ID: |
39434313 |
Appl. No.: |
12/285678 |
Filed: |
October 10, 2008 |
Current U.S.
Class: |
204/406 |
Current CPC
Class: |
G01N 27/48 20130101 |
Class at
Publication: |
204/406 |
International
Class: |
G01N 27/26 20060101
G01N027/26 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 2, 2007 |
FR |
0707720 |
Claims
1. A multichannel potentiostat comprising a reference terminal, a
counter-electrode terminal and at least two working terminals
respectively designed to be connected to a reference electrode, a
counter-electrode and at least two working electrodes of an
electrochemical cell, a first regulating circuit to apply a first
predefined setpoint voltage between the first working terminal and
the reference terminal, a second regulating circuit to apply a
second predefined setpoint voltage between the second working
terminal and the reference terminal, a control circuit of the
counter-electrode voltage applied to the counter-electrode
terminal, said control circuit comprising a first input terminal
connected to a predefined potential and a second input terminal to
which a regulating voltage representative of at least one of the
voltages of the working terminals is applied.
2. The potentiostat according to claim 1, wherein the predefined
potential is ground.
3. The potentiostat according to claim 1, wherein the predefined
potential is the mean of the potentiostat supply voltages.
4. The potentiostat according to claim 1, wherein the predefined
potential is the mean of the limit voltages of the electrochemical
window of the electrolyte.
5. The potentiostat according to claim 1, wherein the setpoint
voltages are independent from one another.
6. The potentiostat according to claim 1, wherein the regulating
voltage is constituted by a combination of the voltages applied to
the working terminals.
7. The potentiostat according to claim 1, wherein the regulating
voltage is constituted by the mean of the voltages applied to the
working terminals.
8. The potentiostat according to claim 1, wherein the regulating
voltage is constituted by the working voltage applied to one of the
working terminals.
9. The potentiostat according to claim 1, wherein the regulating
circuits comprise a first input connected to the reference
terminal, a second input connected to the corresponding setpoint
terminal, and an output connected to an input of a measuring
operational amplifier which has a second input connected to the
corresponding working terminal.
10. The potentiostat according to claim 9, wherein the
counter-electrode voltage control circuit is formed by an
operational amplifier having an inverting input forming the second
input terminal of the control circuit and a non-inverting input
forming the first input terminal of the control circuit.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates to a multichannel potentiostat
comprising a reference terminal, a counter-electrode terminal and
at least two working terminals respectively designed to be
connected to a reference electrode, a counter-electrode and at
least two working electrodes of an electrochemical cell, the
potentiostat comprising predefined setpoint voltages and first and
second regulating circuits to apply setpoint voltages respectively
between the first and second working terminal and the reference
terminal.
STATE OF THE ART
[0002] Electrochemical cells are very commonly used in a wide range
of fields of analysis. As a general rule, in an analysis device, an
electrochemical cell is associated with a potentiostat which
performs two essential functions. It imposes a predefined potential
difference, i.e. a setpoint voltage, between a working electrode
and a reference electrode of the electrochemical cell. At the same
time, the potentiostat measures the current flowing between the
working electrode and a counter-electrode of the cell.
[0003] Multiple potentiostat architectures exist depending on the
complexity of the studies and/or of the phenomena to be analyzed.
Single-channel potentiostats associated with a single working
electrode and multichannel potentiostats associated with several
working electrodes already exist. In the category of multichannel
potentiostats, analysis device potentiostats having one reference
electrode for each working electrode and analysis device
potentiostats having a single reference electrode for several
working electrodes can be differentiated, whether the potentiostat
is used with one or more electrochemical cells. Within the category
of analysis devices having one reference electrode for several
working electrodes, a distinction can also be made between devices
in which the counter-electrode and reference electrode are combined
in the same electrode and devices in which these electrodes are
separate.
[0004] The article by Frey et al. "Design of an Integrated
Potentiostat Circuit for CMOS BIO Sensor Chips", Proceeding of
ISCAS, vol. V, 2003, p 9-12, describes the use of a potentiostat
associated with two working electrodes, a reference electrode and a
counter-electrode. In the corresponding analysis device, the
reference electrode voltage is controlled by means of an
operational amplifier having an input connected to the reference
electrode and an output connected to the counter-electrode, whereas
distinct setpoint voltages are imposed for the two working
electrodes. Moreover, this device is of limited interest as the
setpoint voltages applied to the two working electrodes are
necessarily of opposite signs (one is positive whereas the other is
negative).
[0005] This type of multichannel device with a separate
counter-electrode and reference electrode is not able to study
complex mechanisms, for example different oxidation reducing
species mixed within one and the same electrolyte and able to react
with one another. In this type of device, the output voltage range
is not optimized with respect to the supply voltage range, which
limits their interest.
OBJECT OF THE INVENTION
[0006] The object of the invention is to provide a potentiostat
that in particular enables cyclic volt-ampere metering to be
performed with an optimized available measuring range.
[0007] According to the invention, this object is achieved by the
fact that the potentiostat comprises a control circuit of the
counter-electrode voltage applied to the counter-electrode
terminal, said control circuit comprising a first input terminal
connected to a preset potential and a second input terminal to
which a regulating voltage representative of at least one of the
working terminal voltages is applied.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Other advantages and features will become more clearly
apparent from the following description of particular embodiments
of the invention given for non-restrictive example purposes only
and represented in the accompanying drawings, in which:
[0009] FIG. 1 schematically represents a particular embodiment of a
potentiostat according to the invention.
[0010] La FIG. 2 represents a particular embodiment of a
potentiostat according to the invention in greater detail.
DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
[0011] As illustrated in FIG. 1, potentiostat 1 comprises a
reference terminal 2, a counter-electrode terminal 3 and at least
two working terminals 4 and 5, respectively designed to be
connected to a reference electrode REF, a counter-electrode CE and
at least two working electrodes T1 and T2 of an electrochemical
cell which are all immersed in the same electrolyte. Potentiostat 1
is of multichannel type as it presents several working electrodes
for one reference electrode. The potentiostat is supplied by supply
voltages V+ and V-.
[0012] In conventional manner, the reference electrode is adjusted
to a reference potential V.sub.REF, each working electrode is
adjusted to a different working potential, respectively V.sub.T1
and V.sub.T2, and the counter-electrode is adjusted to a
counter-electrode potential V.sub.CE.
[0013] Potentiostat 1 enables a predefined setpoint voltage,
respectively first V.sub.C1 and second V.sub.C2, to be applied
between one of working terminals 4, 5 and reference terminal 2.
Each working electrode therefore has a working potential (V.sub.T1,
V.sub.T2) that is proper to it and which depends on the setpoint
voltage that is assigned thereto and on the reference electrode
potential.
[0014] Reference terminal 2 is preferably connected by means of a
follower assembly 10 to a first input terminal of two regulating
circuits 7 and 9, respectively associated with working terminals 4
and 5. Each regulating circuit also has a second input terminal
connected to a corresponding setpoint terminal to which the
associated setpoint voltage V.sub.C1, or V.sub.C2 is applied.
Regulating circuits 7, 9 thereby enable a predefined setpoint
voltage, V.sub.C1 or V.sub.C2, to be applied between each working
terminal 4, 5 and the reference terminal such that:
V.sub.T1=V.sub.C1+V.sub.REF
V.sub.T2=V.sub.C2+V.sub.REF
[0015] In the particular embodiment illustrated in FIG. 1, the
inverting input of a first measuring operational amplifier 6 is
connected to working terminal 4 and, via a resistor R1, to the
output of operational amplifier 6, which is connected to a first
measuring output S1 of the potentiostat. The non-inverting input of
operational amplifier 6 is connected to the output of first
regulating circuit 7.
[0016] In the same way, the inverting input of a second measuring
operational amplifier 8 is connected to working terminal 5 and, via
a resistor R2, to the output of operational amplifier 8, which is
connected to a second measuring output S2 of the potentiostat. The
non-inverting input of operational amplifier 8 is connected to the
output of second regulating circuit 9.
[0017] This assembly therefore enables the potentials of the two
working electrodes (T1, T2) to be set independently from one
another so that the potential difference between one of the working
electrodes and the reference electrode is determined by the
corresponding setpoint voltage (V.sub.C1, V.sub.C2). The setpoint
voltages (V.sub.C1, V.sub.C2) are therefore independent from one
another.
[0018] This assembly further enables signals representative of the
value of the currents flowing in the two working electrodes (T1,
T2) to be obtained on measuring outputs S1 and S2. The maximum
(VSmax) and minimum (VSmin) voltages that can be obtained on
outputs S1 and S2 define the measuring range VSmax-VSmin for each
of the outputs.
[0019] Potentiostat 1 also enables the counter-electrode potential
V.sub.CE to be set, via a counter-electrode voltage control circuit
11, so as to adjust for example the potential of a working
electrode or the mean of the working electrode potentials to a
preset potential V.sub.P. It is thus possible to vary the potential
of working terminals 4, 5 and therefore of working electrodes
V.sub.T1, V.sub.T2 by means of the counter-electrode, thereby
increasing the measuring range. The potential V.sub.P can for
example be ground or advantageously the mean of the potentiostat
supply voltages, or even more advantageously the mean of the limit
voltages of the electrochemical window of the electrolyte. The
preset potential V.sub.P can moreover also be a potential that is
fixed by means of an additional terminal of potentiostat 1 in the
same way as for potentials V.sub.C1 and V.sub.C2.
[0020] Counter-electrode potential V.sub.CE, associated with
counter-electrode terminal 3 is fixed by the output of control
circuit 11, which comprises a first input terminal connected to the
potential V.sub.P and a second input terminal to which a regulating
voltage V.sub.TX representative of at least one of the voltages
(V.sub.T1, V.sub.T2) of working terminals (4, 5) is applied.
Regulating voltage V.sub.TX can be constituted by a voltage applied
to a working terminal or a combination of the different voltages
applied to the working terminals, for example the mean of the
voltages applied to the working terminals. Control circuit 11
regulates the counter-electrode voltage V.sub.CE so that
V.sub.TX-V.sub.P=0. Practically, control circuit 11 has a first
input terminal connected to potential V.sub.P and a second input
terminal connected to the output of at least one of regulating
circuits 7 and 9. Preset potential V.sub.P is therefore a potential
towards which the potential of a working electrode or of a
combination of the working electrode potentials, for example the
mean of the working electrode potentials, is maintained by
controlling the counter-electrode potential V.sub.CE.
[0021] In a first alternative embodiment, it can be sought to make
the potential of second working electrode T2 tend to the potential
V.sub.P (V.sub.T2-V.sub.P=0). The regulating voltage V.sub.TX is
then constituted by working voltage V.sub.T2 applied to associated
working terminal 5. In this way, counter-electrode potential
V.sub.CE is modulated so that the potential of second working
electrode V.sub.T2 tends to the potential V.sub.P. Practically, the
second terminal of control circuit 11 is then preferably connected
to the output of regulating circuit 9 (FIG. 2).
[0022] In like manner, in a second alternative embodiment, it can
be sought to make the potential of first working electrode T1 tend
to the potential V.sub.P (V.sub.T1-V.sub.P=0). Regulating voltage
V.sub.TX is then formed by working voltage V.sub.T1 applied to the
associated working terminal 4. In this way, counter-electrode
potential V.sub.CE is modulated so that the potential of first
working electrode V.sub.T1 tends to the potential V.sub.P.
Practically, the second terminal of control circuit 11 is then
preferably connected to the output of regulating circuit 7.
[0023] In a third alternative embodiment, it can be sought to set
the potential V.sub.P equipotentially between the potentials of
working terminals 4, 5. Regulating voltage V.sub.TX is then
constituted by the mean of voltages V.sub.T1 and V.sub.T2 applied
to working terminals 4 and 5.
[0024] In practice, the second terminal of control circuit 11 is
advantageously connected to the output of the regulating circuit or
circuits 7, 9 associated with the electrode or with the plurality
of electrodes whose potential is to be made to tend to the
potential V.sub.P.
[0025] As illustrated in FIG. 2, each regulating circuit 7, 9
advantageously comprises an operational amplifier 12, 13 connected
as a summer. In the particular embodiment illustrated in FIG. 2,
the inverting input of operational amplifier 12 is connected to the
corresponding setpoint terminal (V.sub.C1) via a resistor R3 and to
the output of operational amplifier 12 by a resistor R4. The
non-inverting input of operational amplifier 12 is connected via a
resistor R5 to the output of the follower assembly 10 connected to
reference terminal 2, and is grounded via a resistor R6. The
potential applied to the output of operational amplifier 12, i.e.
to the output of regulating circuit 7, is therefore a function of
the reference potential V.sub.REF and of the corresponding setpoint
voltage V.sub.C1.
[0026] In like manner, the assembly of regulating circuit 9 enables
the potential V.sub.T2 of corresponding working electrode T2 to be
set as a function of the corresponding setpoint voltage
V.sub.C2.
[0027] Furthermore, in FIG. 2, the output of operational amplifier
6 is advantageously connected via a resistor R7 to the inverting
input terminal of an operational amplifier 14, which is feedback
connected by means of a resistor R8 and whose output is connected
to measuring output S1. Resistor R8 thereby connects the inverting
input and the output of operational amplifier 14. The non-inverting
input of operational amplifier 14 is grounded via a resistor R9,
and is connected to the output of operational amplifier 12 via a
resistor R10. Operational amplifier 14 thereby enables a voltage
representative of the current value flowing through working
electrode T1 to be obtained on measuring output S1.
[0028] A similar assembly can be performed from outputs of
operational amplifiers 8 and 13 to obtain a voltage representative
of the current value flowing through working electrode T2 on
measuring output S2.
[0029] In the particular embodiment illustrated in FIG. 2, control
circuit 11 of counter-electrode voltage V.sub.CE comprises an
operational amplifier 15 that has an inverting input connected to
the output of operational amplifier 13 via a resistor R11. This
inverting input is also connected to the output of operational
amplifier 15 via a resistor R12 and capacitor C connected in
series. The non-inverting input of operational amplifier 15 is
connected to the potential V.sub.P by a resistor R13. Control
circuit 11 of counter-electrode voltage is thereby formed by an
operational amplifier 15 having an inverting input that constitutes
the second input terminal of control circuit 11 and a non-inverting
input that constitutes the first input terminal of control circuit
11. In this particular embodiment, the regulating voltage V.sub.TX
is constituted by the working voltage V.sub.T2 applied to working
terminal 5, and the counter-electrode potential V.sub.CE is set
such as to make the potential of second working electrode V.sub.T2
tend to the potential V.sub.P (V.sub.T2-V.sub.P=0).
[0030] In an alternative embodiment, not represented, to make the
potential of first working electrode V.sub.T1 tend to the potential
V.sub.P (V.sub.T1-V.sub.P=0), the inverting input of operational
amplifier 15 is connected to the output of operational amplifier
12.
[0031] In a third alternative embodiment, not represented, the
outputs of operational amplifiers 12 and 13 are connected to the
inputs of a summer having its output connected to the inverting
input of operational amplifier 15. In this case
V.sub.TX=(V.sub.T1+V.sub.T2)/2. Counter-electrode potential
V.sub.CE is then set such as to place the potential V.sub.P
equipotentially between the potentials of the two working
electrodes T1 and T2.
[0032] In this way, the potentiostat according to the invention
enables the counter-electrode potential to be controlled thereby
optimizing the output voltage range with respect to the supply
voltages range of the potentiostat. This approach can be
particularly interesting if a constraint exists on the supply
voltages.
[0033] The potentiostat further enables independent setpoint
voltages to be applied between the working electrodes and the
reference electrode, which means that a positive setpoint voltage
between a working electrode and the reference electrode and a
negative setpoint voltage between another working electrode and the
reference electrode can be applied simultaneously.
* * * * *